Temperature control in regeneration of contact agents



March 13, 1951 J. w. MOORMAN ET AL TEMPERATURE CONTROL IN REGENERATION 0F CONTACT AGENTS Filed May 26, 1949 INVENTORS JOSEPH W. MOORMAN BY LOUIS J, KELLY g :7 of W I 1 I ATTORNEYS Patented Mar. 13, 1951 I TEMPERATURE CONTROL IN REGENERA- TION' OF CONTAGT AGENTS" Joseph Mo'orman', Alpine and Louis J. Kelly, TenaflnN. l, assignors id- The. M. W. Kellogg Company, Jersey City N; JJ.,. a corporation of Delaware,

Applik:ation M'ay 26, 194$; sonar 1%.. 9515481 I The present invention relatesin general to improvements in the regeneration of powdered.- catalyticmaterials which have becomespent in use by reason of a deposit of combustible material thereon, particularly as applied to the catalytic conversiorrof hydrocarbons by a continuous cyclic process wherein said particles of a catalytic material and vapors of the hydrocarbons undergoing conversion are contacted aconversionzone, spent catalyst particles are separated from" the vaporou-s' conversion products and thereafterregenerated forreuse by' contacting them with an oxygen-containing gas under suitable conditions to cause combustion or the carbonaceous deposit thereon. The contacting occurs in a regenerati'on' zone in whichthe catalystparticles are maintained in afluidized' state and aninterface is maintained between a lower dense phase and an upper light phase by the upward passage of the regenerating gas through the regenerating zone. More particularly, this invention discloses a method for controlling the temperature of the dense phase mass of catalyst in the regeneration zone; the cooling" is accomplished by maintaining" the interface level at a predetermined elevation such that the withdrawn overhead phase contains the amount of catalyst required forcool ing' the dense phase tothe desired temperature.

application is; a continuation i n-partl of our copending application Serial No. 775,050; filed September 19, 1'94'L Heretofora variousprocesses havebeen pro posed for effecting regeneration operations of: this type. Becauseof the highly exothermic character of the combustion reaction involved, and the sensitivity of the catalytic material's'at high temperatures the. provision of a satisfactory regenoration process has been attended. with many diffi'cul-tiea. Furthermore. conversion reactions of this type are; necessarily practiced commercially in'units of: considerable size and capacity and, accordingly; the: problem of minimizing the size and. cost of the necessary equipment? is of" outstanding importance;

The primary object of the present invention is the; provision. of a regeneration process wherein thezgtemperature of the: regeneration. operation andgthe rate of combustion may be readily and satisfactorilymaintained within desired limits,

andi'one which may be practiced. in apparatus substantially reduced size; and consequent? cost ofconstructiorr compared to the apparatus rein: proceduresheretofore. proposed.

' Brion to the presentmentiomit:hasbeenpro, V t efiecttha cit spenizpowdemfi' V 5, Glaims. (o1. ice-52)! or finely divided. cracking catalyst, and similar mat'efi'a-IS; by a procedure involving. the suspension of the catalyst particles in an oxygen-containing; gas-and the passage of. the suspension through a regeneration zone: underconditions: adapted to cause: combustion.- oi the deactivating depositioi' carbonaceous materiala It has-1 been further proposed-t, inaconnecticir with this method, to control-l the temperature of? the regeneration zone by recycling' thereto: a portiomof theregenerated, cataa lyst; after cooling portion to a suitable temin temperature at the;- eoo-led recycled catalyst stream:v Iii-lathe; premously'prop'osed.method; however, theucoolingz catalyst-stream-has beerrw H drawn from the dense phase mass: oi. catalyst m within. the: regeneration: zone-,3 cooled to the: de-

sired. cooling temperature; and. recycled;- to the regeneration: zone; the: gaseous; reaction products have" ordinariity'been. withdrawn from; the 110E of the regeneration chamber; afiter separation by settling on cyclone, separators of all; the catalyst po'ssibla. Iiraccondancewith; thismodeofoperatimigtthewinteriace betweemthe lower dense phase the; upper: dilute ph se: is; usu tlll maintained at at'level feet onmore; belowthea point of withdrawal-Z of: the regeneration gases, The: rowson for this/is that about 152 feet seems to be the suitable: settling; space for: the, de-en,- trainment of catalyst of the customary particle size from: gases moving: at-:-the velocity which: is ordinarily employed; in fluidized catalyst; system. The velocities are usually; between 12.0; and feet per minute. Eneqnentlm. cyclone separators; con

s-tructedlto Withstand? high: temperatures: are. snsa dilute: phases settling regional the regeneration zone It'- haszv'al'sos'beemproposedzto remove the: relatimely small: amount of. catalyst remaining: in: the wi thdmawm regeneration gases by first cooling to; a; temperature 0t: about; 650 F: or; lower and: than: passing-r them through separattors, the prelnninarycooling being required. he

c nsecration zone. imme 3 there is a minimum height of dense phase below which the interface must not fall if adequate regeneration is to be accomplished; but above this minimum height there is a range in which any level of operation is quite satisfactory except that higher levels will result in more catalyst carryover because of the reduction of settling space as the interface approaches the point of Within this satisfactory operating range the amount of catawithdrawal of regeneration gases.

lyst carryover can be increased or diminished as a desired by raising or lowering the interface level. The interface levels required in a particular case will depend in part upon such predetermined factors as gas velocities, particle sizes, apparatus dimensions, and, in part, on the behavior of a particular piece of apparatus as" determined-from '1 case but with a method of operation which may be applied to a specific case by those skilled in the art.

Moreover, it should be noted that the interia'ce referred to is not as sharply defined as the surface of a body of water or the like, but is really a horizontal region having perceptible thickness-a region in which the density of catalyst decreases with elevation at a rate which is much greater than in the regions-above and below it. In short, the interface is a'discontin'uity region of sudden density change between alower' dense phase and an upper dilute phase; However, in spite of the fact that the interface is not exactly like that between a liquid and a gas, it is readily determinable and is one of the properties of fluidized catalyst systems which distinguishes them from other solid-vapor contact systems. When the present method of regenerator cooling is employed all of the withdrawn dilute phase is cooled to a predetermined temperature and is transferred to a cooled catalyst hopper in which the catalyst is separated and accumulated. If desired, some catalyst may be separated from the dilute phase before its passage through the cooler,

provided that the catalyst remaining in suspen- 'sion is sufiicient to accomplish the subsequent cooling required. Furthermore, the discharge temperature of the cooler may be sufficiently low to permit the use of separating means not capable of operating at high temperatures, Cottrell pro-'- cipitators, for example. Cooled catalyst is continuously withdrawn from the cooled catalyst hopper and entrained in the regenerating gas being introduced upwardly into the bottom of the regeneration zone. The temperature at which the regeneration zone isto operate can be establ shed by adjustment of the recirculating catalyst valve. Increasing the flow of'cooled catalyst from the cooled catalyst hopper through this valve causes the interface within the regeneration zone to rise and the amount 'of carryover catalyst to increase. Reducing the flow of cooled catalyst through the recirculating catalyst valve results in the fall of cooled catalyst and aconsequent reduction in carryover catalyst and in dense phase temperature. After the system has been placed in operation at a given temperature, this temperature'can-be maintained by continuously adjusting the recirculating catalyst valve to maintain the interface level which corresponds to a particular temperature; If desired, this may be accomplishedautomatically by instrumentation for controlling the :valve so tion with the drawing and the five tables.

as to maintain a predetermined interface level within the regeneration zone in accordance with methods and apparatus for bed level maintenance well known to those familiar with the fluidized catalyst art.

Various other specific features and objects and advantages of our invention will be apparent from the detailed description given in connec- The drawing discloses the type of apparatus in which the method of the present invention may be practiced. The tables describe the conditions of operation. Particularly, Table V relates to a mode of operation in which the only cooler in the system is that which is employed for cooling the dilute phase withdrawn from the regeneration zone. Tables I to IV and methods of operation described in connection therewith relate to modifications in which the method of the present invention is of less importance and is used with other cooling means. 1

In the drawings: ,.Figure l is a diagrammatic illustration of a suitable arrangement of apparatus and process flow for the practice of the invention as applied to the catalytic conversion of high boiling .hy-; drocarbons to low boiling hydrocarbons within the motor fuel boiling range. -Figure 2 is a sectional-view taken along line Ii -II of Figure l.

1 Figure 3 is a diagrammatic illustration-of a modified form of apparatus for the practice of the embodiment of the invention involvingthe cooling of a recycled stream of regenerated-cattl lyst.

Following the process flow illustrated in Fig. 1 of the drawings, a suitable feed stock, for example, a high boiling hydrocarbon fraction such as a reduced petroleum crude, gas oil, or the like, is introduced through line I by pump 2 into heating coils 3 in furnace 4, wherein it is vaporized and heated to a temperature approximately that required for the subsequent conversion operation. In the case of a reduced crude charging stock, a portion of the feed as discharged from the furnace will remain unvaporized. Steam may be suitably introduced into the furnacecoil at intermediate points through lines 5 to facilitate vaporization, and sufiicient pressure is maintained at' the furnace outlet to prevent coking of the coil. From furnace t, the heated charge passes bytransfer line 6 to the base of a regenerated catalyst standpipe l or other suitable source of active catalytic material. From standpipe 1,- hot active catalyst is introduced at a rate controlled by valve 8 into the feed mixture, the heat content of the regenerated catalyst stream being sufiicient tocompletely vaporize the oil, not vaporized in the furnace, provide the heat of cracking by superheating the vapors, and to discharge the products from the reactor at the desired end con-'- version temperature, for example about 950 F.

'In the case of a reduced crude charging stock,

the vaporization of the oil at this point includes a partial decomposition or cracking of this nonvolatile component of the feed. Additional steam may suitably be introduced through line 9 to form .a gaseous suspension with the catalyst discharged through valve 8. The mixture of catalyst particles and vapors passes through line Ill and inlet ll into the lower part of reactor l2. Re-

actor !2 is a vessel in the form of a cylinder or other suitable shape having a relatively great cross-sectional area compared to the cross-sec- .tional area of the. vapor inlet. line Ill, and these relative proportions cause a corresponding. reduction inthe velocity of the vapors after, their passage from inlet line H: into reactor I22? The velocity of the vapors in reactor 12 preferably'is maintained. within such limits as to produce therein a highly turbulent and concentrated or dense phase of the catalyst, similar to thecondltion maintained in zone A of the regenerator. However, any conditions adapted to produce suitable contact between the catalyst particles and the vapors undergoing conversion maybe utilizedin the conversion zone with reference to the practice of the present invention.

The dense turbulent catalyst phase (zone A) extends only partially up the reactonthb upper horizontal level thereof being indicated-by dotted line I3. Zone B, the reactor space alao ethls level I con t tutes a catalyst-vapor disengaging space, a relati ely smallproport on ofsthe total catalyst introduced being carried out. overhead with the vaporous conversion products from zone B t rou h vapor outlet 14. Used or spent catalyst suitably is withdrawn from the conversion zone b a catal t withdrawal passageway '5 opening directl into the dense catalyst phase in Z The relativelv cros -sectionalareas of catalyst outlet 15 and reactor I2 are shown [in Fig. 2. A suita le inert as such as steam is introduced in t e lower portion of the catal st withdrawal pas a eway l5 thro h line 16 todi place orstrip hydroc rbon vapors mixed or entrained with the separated catalyst and to maintain the catalyst therein in an aerated flowable cond tion. Cataly t is w thdrawn from pa sagewaydfi in two streams throu h catalyst standpipes 11 and I8 to which an inert aeratine medium isennplied by means of uita le inlet lines (notzdllu trated) distr but d at uitable interval aloneit eir length to m intain the catal st flowing therethrough in a den e but readily flovvable state.

The vanorous conversion products containing a relati ely small proportion of thetotal catalyst fed to the reactor, that is. an amount of the order of abo t 15 per cent or less, pass overhead from zone B through outlet '4 to a suitable gas- .solid separating system. This se arating sys- 22. which preferably extend as. indicated into the reactor .9. short di tance below theupper level I3 of the den e catalyst phase. Tailpipes 2| and Z2 likewise may be suitably provided with inlet lines,

not shown. distributed at suitable intervals along 3 their length for introducing an aerating medium thereto to maintain the catalyst passing therethrough in a fiowable conditiong-j The vaporous conversion products withdrawn *sfrom the final cyclone 2.0 through outlet line -2-3are passed to a suitable products recovery sy l .8m, such as a fractionating tower or the like, wherein the products are separated into the desired fractions, such as gasoline, fuel .oil, and cycle oil. The small amount of catalyst remaining vapors withdrawn through line 23 may be recovered by pardrawnfrom the hoppers throughitailpipes 2 I and r manifold line 25. The air necessary for regenertially condensing these vapors, thereby conced trating this residual catalyst in the hcavy'iboidmg condensate which may be recycled to the re actor hr h feed line I as described in the patent to Belchetz, No. 2.374.073, granted April 17, 1945.

In appended Table 1 there is given an illustra 'tive example of suitable dimensions for reactor ['2 and of operating conditions for the conversion of a reduced crude petroleum oil over a powdered alumina-silica type of cracking catalyst of the activated clay Super-Filtrol" variety, into low boiling constituents consisting of a large proportion of low boiling hydrocarbons within the gasoline boiling range and. characterized by their high octane value. In this particular case the reactor was designed to process 16,000 bbl/day of a Mid-Continent reduced crude having a gravity of 23 degrees A. P. I. to produce the following products in the yield indicated:

10c R. V. P. gasoline--......-,vo1. percent" 42.5 No. 3 heating oil o-- "do 11.2 Heavy gas oil- ..,..cunpflcndo u, 32.8 No. 5 fuel oil-.. "dog". 72 Excess butane g do,,g 5.5 Dry gas" weight percent... 5.5 Coke -c -do l. 4.2

Table I Reduced crude oil feed bbl./day 16,000 Steam feed (based on oil 7 teed) wt. percent 10 Reactor dimensions:

Zone A- Height it y 18 Diameter -ft 19.5 Height f,t 8

Zone B- Diameter "it" 19.5

Feed wt. ratio of catalyst to oill 7.5:]. Oil-vapor temp. (at furnace outlet) F 900 Regenerated catalyst temp. (standpipe .1) F 1050 Catalyst concentration (average)- (a) Zone A lbs./cu.ft 15,7

(b) Zone B lbs./cu. ft 1.0 to 1.5

(0) Catalyst draw-01f line 15 l -,1bs./cu. ft... 18.5

(d) Vapor line 2.3 grains/cu. it. 6

' Vapor velocities Zone A..-.. cc. ft./secm 1.5 Zone B l, "ft/sec" 2.06 Oil contact time (average) seconds,.. 1.0 Catalyst contact time (average) do..... 15.6

Ratio of Wt. of oil fed/hr. to wt. of

catalyst in zone A. 3.09 Reaction vapor temp. at outlet from 0 zone B Fc- 945 Reactor pressures (gauge)-- (a) Inlet to zone A lbs./sq. in 10.0 (b) Outlet from zone B. lbs./sq in..- 8.0

- such as air issupplied to the regenerator by any suitable means such as air compressor 24 through lyst. A is indicated by dotted line 35 and the physical .,A', the dense catalyst phase.

cooler or heat. exchanger 3| wherein it is cooled toa relatively low temperature, preferably below Ithe ignition temperature of the carbonaceous J deposit, and .then' passes therefrom through outletlinel32 into'the-baseof'the regenerator 33. Asuitable cooling medium is circulated to exchangerSl through line 34. The gaseous suspension of catalyst in line 28 is passed directly to the lower portion of the regenerator 33, without cooling. Alternatively, all of the spent catalyst may be passed by line 21 through ex changer 3| and the total stream cooled to a somewhat higher temperature corresponding to that resultin from mixing the streams in lines 32 and 28 The use of two lines as shown is greatly preferred, however, since the flexibility of control is greatly enhanced by diverting a suitable amount from one stream to the other as required.

The quantity of regenerating fluid introduced into the regenerator is maintained within such limits that the upward velocity of the gases through the regenerator produces a highly concentrated and turbulent dense phase of the cata- The upper level for this dense phase zone characteristics of this phase are similar to those of dense phase zone A present. in the reactor l2. Zone B, the space in the regenerator above level 35, similar to zone B above level 13 of the reactor, constitutes a catalyst-vapor disengaging space, this zone preferably extending a sulficient distance down from the entrance to outlet 36 sothat only a relatively small portion of the total catalyst introduced is carried out overhead .with the fiuegas from zone B through outlet line 36.

Regenerated catalyst is suitably withdrawn lfrom the regeneration zone by a catalyst withdrawal passageway 3'! opening directly into zone A stripping medium, such as steam, may be supplied to passageway 31 by line 38 in amount suiiicient to strip ,the withdrawn regenerated catalyst from entrained oxygen-containing gas, or any suitable ,aerating medium may be used to maintain the body of catalyst therein in a dense but readily fi owable condition. From passagewayor compartment 3'I-regenerated catalyst is forwarded by catalyst standpipe l to the conversion stage 'as previouslydescri-bed.

Catalyst contained in the flue gas suspension withdrawn overhead through line 35 may be re- In illustrating suitable operating conditions "maintained in the regeneration stage pursuant .to the present invention, appended Table II onditions. corresp n ing t an m r t n t conversion stage as'given in Table I fllable I I is on the basis of no temperature control duty being performed by the catalyst withdrawn overhead through line36, as for'example, when this 'catalyst is returned at substantially the same temperature as withdrawn, or is forwarded to some part of the system other than the regeneration zone, or is negligible in amount; Table IV, given hereinafter, illustrates the application of the invention when the stream of catalyst withdrawn overhead and recycled to the regener'ator' isutilized to effect a substantial degree of temperature control duty.

7 Table II Regenerator dimensions: g

Zone A' k i 'Y w ft 7 Diameter ft 3.05

-ZoneB' Height ft 16 -Diameter ft 30.5 Spent catalyst (lines 1! and l8) 7 lbs./hr 1,617,355 Cooled spent catalyst (line 32) lbs./hr 1,294,420 Spent catalyst (line 23) lbs./hr 322,935 Temp. of cooled spent catalyst (line 32) F 785 to 740 Temp.- of spent...catalyst .(line 2B) -r F 940 to 985 Temp. of regeneration zone F 1050 Catalyst concentration (average)-- r (a) Zone A slbs./cu.f t 14.8 .(b) Zone B'- lbs./cu.ft 1.0 to 1.5

=.(c) .Catalyst draw-ofi line lbs./cu.ft 18.0 -...(d) Flue gas outlet line 36 grains/cu.f t 400 Gas velocities-a.

Zone A- ft./sec 1.62 Zone B. ft./sec 1.85

Catalyst contact time (average) seconds 120 Regenerator pressures (ga-uge) (cl-Inlet to zone A -lbs./sq.in 5.4

, (12), Outlet from zone B 1bs./sq.in 3.9

ticles of catalyst not disengaged in the zone B may be directed from the top of the regenerator 33 eith er through .a recovery system,,as provided for reactor. 12, or through line '35 to a cooler 39,

.wherein they pass in indirect heat exchange wi h-.a oli s l id ed um circulated b means .,of lines 49, In. connection with the method of the present invention, it should be noted that the. dilute phase passing through cooler 39 emerges fromits outlet at a predetermined cooled catalyst temperature which is substantially constant regardless of variations in the amount of catalyst passing through cooler 39. The cooled catalyst temperature is substantially constant for tl esystem andcooling of the-dense phase the regeneration zone is increased or reduced by; increasing or reclucing the quantity of ree circulated cooled catalyst. The outlet temperature fqrthe dilute phase emerging from cooler 39 may be as low as 650 F. or less in order that Pf e ta n of regeneration st e, s satee -resign n w temp rat let 9 Separators, or the like may be employed for separating catalyst. e

. The mixture of regeneration gases and" entrained solids is directed from the cooler through line 4| to a separator comprising cooled catalyst hopper 2 and cyclone separators connected in series, such as a l and 46, in each or" which a portion of the catalyst is separated from the vapors and returned to thehopper 32. The mixtureirom line 41 enters the side of hopper it and is directed out of the hopper through overhead line 23 to the cyclones. each of the series connected cyclones M and 46 are returned to the hopper 42 through tailpipes 45 and 41', respectively, and overhead line 48 conducts the separator vapors to a stack. QGoled' regenerated catalyst is withdrawn from the bot-- tom of cooled catalyst hopper-4'2 through standpipe 49 controlled by a cooled catalyst valve 59; and is'conveyed back to the" dense phaseA of the regenerator rtathrough line 5|. While passing downwardly through standpipe 49'; the catalyst may be stripped of regeneration gases by the in troduction through lines 52 of asuitable fluid stripping medium, such as steam. It is' convenierit to provide a freshcatalyst charging line ii'a'by means of which fresh catalyst may be in troducedinto the system. Ordinarily, a few tons will be blown into the cooled catalyst hopper t2 once every 24 hours. It" is also convenient to provide a catalyst draw off line 52b by" means of which contaminated cat'alyst'can occasionally be withdrawn from the system amt transported to a waste dump. v

The capacity cf cooled catalyst hopper i2 is a matter to be engineered: for eachparticular system. lfioweve'r, this capacity must be sufficiently large to allow for varying the inventory of cooled catalyst storedin hopper 52' over what'- ever range of quantities maybe required to employ the variousmethods of cooling regenerator 33-. 7

As" Will be described hereinafter in connection with Table V, it is the preferred method of operation for the method; of the present invention that cooler 39- be theonly cooler employed in the system and that the quantity of catalyst cooled. be regulated by controlling the level of the inter face 35. When this preferred method is employed for cooling the regenera-tor, temperature control may be made automatic by control means" 59a which operates valve 5'll'so as to maintain interface 35' at a: predetermined height. means 500 includes a-val've positioner, indicated as VP and twopressure d iiferenti'alf controllers; indicated as PDC J all in accordance" with instrumentation well known in the art: for con trolling a valve inresponse to interface position. I In accordance with one method of operation; the catalyst recovered in the separator and returned to the dense phase of the regenerator through line 55- comprises onl'ythe entrained particles which have failed to be disengaged from the vapors in' zone B and whichhave been ried' overhead through outlet line 36. The amount ofcooled catalyst thus recycled to' the" dense phase-of the regeneration zoneis not su fiic'ient to effect any substantialcooling of thecat'a'lyst' bed as a whole zone A. Pursuant to this method. theprincipalf means for maintaining temperatures" within the desired range in the regenerator' 33, therefore. is by the use of coller' 3|, which coolsanydesired proportion of the spent catalyst from the reactor l2 before'its introduction to the regeneration zone.

Separated catalyst particles from v Another method of o"eration i nvolves the pro; cooling of both the. incoming spent catalyst stream directed throughline 32 to the regenerator 33 and a streamoff recycled regenerated catalyst Withdrawn from the zone B of the regenerator 33 through line 36* and returned tothe zone A of the regeh'erator through line 51, as illus trated in Fig. 1. In the practice of such modifica' tion the stream of regenerated ca-talyst withv drawn overhead from zone B is suitably cooled in the heat exchanger- 39 toa temperature suinciently' low to cause the recycled stream of reigenerated catalyst to exert a substantialmeasure of temperature control upon the dense bed of catalyst when it is' returned to the lower portion. of A through line 5-l-. Table: III which follows; illustrates the. practice. of the invention assor modified, as applied; to a regeneration stage cor responding to a. conversion stage in accordance with the conditions given in Table. I. I v

It is apparent that the major portion oftermperature control within the regenerator 33 is placed upon the heat exchanger 3-! connected the spent catalyst inlet-line leading from there-; actor I 2' to the regenerator; sincetheamount of. catalystnormallypassing out of the. regenerator through overhead line 36 is relatively small-in comparison with the amountof spent catalyst Control being charged to theiregenerator. To exert anysubstantial temperature control upon the dense? phase bed in zone A, therefore, the recycled: stream of regenerated catalyst must necessarily besubjectedto considerable-cooling. In the illus tra-tive sample set forth in Table III it will be noted that the feed rate of cooled spent catalyst; through line 3-2,to the dense bed of the; regenerator'is more than five times greater" than the feed rate: of cooled regenerated catalyst recycled: to the dense bed of the 'regenerator through line 5|;

Regenerator pressures (gauge) (a) Inlet to zone A lbs./sq. in-.. 5.4

'.(b) Outlet from zone 4 B lbs./sq. in 3.9

. Fig. 3 illustrates a modification in which the operation differs from that described in connection with Fig. l and illustrated by-Table II in that a substantial proportion of regenerated catalyst may be withdrawn from the dense phase of the regenerator and recirculated to the regeneration zone with intervening cooling of the recycled stream. The elements of Fig. 3 which are similar in their function to those described in connection with Fig. l are indicated by similar reference numerals increased by the numeral 100, and hence further detailed description of these elements is believed unnecessary. In this e'mbodiment all the spent catalyst may be forwarded to the regeneration stage in a single stream through line I28. without any substantial or positive cooling of this stream below the temperature at which it is withdrawn from the conversion zone A. Regenerated catalyst for recycling is withdrawn directly from the dense phase through. a withdrawal passageway or compartment I53, similar to passage I31. If desired, however, this compartment may be combined with compartment I31, and two catalyst outlet lines leading therefrom be employed, similar to standpipes II and I8. An aerating medium, such as air or steam, is supplied to compartment I53 through line I54 in amount sufficient to maintain the catalyst therein in a dense but flowable condition. From compartment I53, regenerated catalyst is withdrawn through standpipe I55 at a rate regulated by valve I56, and introduced to transfer line I51 through which it is conveyed by air to a heat exchanger I58 wherein it is cooled to a relatively low temperature, preferably below the ignition temperature of the carbonaceous material, by a suitable cooling medium circulated through lines I59.

Instead of utilizing the circuit comprising ele ments l53, l 55, I56 Il and l58 for the entire burden of temperaturecontrol; duty, the dense phase stream of cooled catalyst may be supplemented by the catalystcarried overhead with the-flue gases through line I36- and returned to the dense phase, after suitable cooling and separation from -the flue gases, through line IEI. Table IV sets forth suitable operating conditions in the application of this modification, described with reference to Fig. 3, to a regeneration operation corresponding to the conversion operation outlined in Table I, exc ept that alower catalyst to oil ratio of 4 to 1 has been employed.

Table IV j Regenerator dimensions:

Zone A'- Height ft 27.5 Diameter ft 23 Zone B' Height ft Diameter ft 27 Spent catalyst (line I28) lbs./hr 623,490 Temp. spent catalyst (line I28) F 895 Recycled catalyst (line I51) lbs./hr 637,000 Temp. recycled catalyst. (outletof..-

I58) F 595 Recycled catalyst .(line. 1.51 lbs., hr 25,000 Temp. recycled catalyst (line ISI) F 595 Temperature of regeneration zone, F 1000 Catalyst concentration (average) -v,

(a) Zone A lbs./cu.ft 14.8

(22) Zone B lbs./cu.it.. 1.0 to 1.5 (0) Catalyst draw-off line I31 lbs./cu. ft 18 Gas velocities- Zone A ft./sec 1.8 Zone B ft./sec 1.7 Catalyst contact time (average) seconds 416 Regenerator pressures (gauge)- I (a) Inlet to zone A lbs./sq. in 7.0 (b) Outlet from zone B lbs./sq. in 3.0

In the diiierent illustrative embodiments of the invention described with reference to Figs. 1 and 2, in each instance the upward velocity of. the oxygen-containing gas through the regeneration zone is maintained sufiiciently low to cause a relatively dense and concentrated catalyst phase to form in the regeneration zone, and sufficiently high to produce a high degree of turbulence of the catalytic particles comprised in the dense phase with the consequent maintenance of a substantially uniform temperature therein. In addition, the catalyst is introduced to said dense phase after precooling to a temperature substantially lower than the substantially uniform temperature maintained in the regeneration zone. The precooled stream of catalyst entering the regenerator may suitably be cooled to a temperature below the ignition temperature of the carbonaceous deposit thereon without resulting in a subcooling of the regeneration zone to a point at which combustion would either cease or proceed at an unsatisfactorily low rate.

The range of upward gas velocities through the regeneration zone adapted to produce the required highly turbulent dense catalyst phase in this zone is dependent upon such physical characteristics as the particle size and density of the catalyst particles employed and may readily be determined experimentally for any particular choice of catalyst or contact agent. In the case of a powdered or finely divided cracking catalyst, such as the activated clay Super-Filtrol consisting largely of particles of mixed sizes smaller than 100 microns, the preferred range resides within 0.5 to 6.0 ft/second and preferably within the more restricted range of 1.0 to 3.0 ft./second.'

A general advantage flowing through the practice of the invention is the reduction in quantity. of catalyst circulated through the heat exchanger in order to accomplish the desired temperature control. A further highly important advantage is the reduction in the quantity of catalyst cooled and recycled to the regeneration zone with consequent important savings with respect to cost of circulating this catalyst and reduction in the size and cost of the equipment including the cooler and auxiliary lines. I

In the various modifications illustrated by Figs. land 3, in which the entrained catalyst carried overhead from the regeneration zone with the gaseous products of regeneration is cooled and subsequently returned to the regeneration zone, the maintenance of temperature control in the regenerator within the desired range is accomplished by the employmentof two separate coolingsystems. InFig. 1 for example, coolers 3i and spent catalyst stream is omitted, but a cooler I58 is provided for recycling a stream of catalyst withdrawn-from the densephase of the regenera= tor. in'accordance with the present invention, it is proposed to effect economies in construction andoperation by eliminating one of the coolers and placing the burden of temperature control upon a single cooler. catalyst is withdrawn from the regeneration zone for passage concurrently with the gaseous products of regeneration through a common cooler, suchas'the cooler 39 of Fig. 1, and, after separating the catalyst from the gases, the cooled catalyst is returned to the dense phase of the regeneration zone. In 'such modification the cooler 3I,-.is omitted. l One method for passing additional catalyst from the regeneration zone to the cooler is to cause the gases-leaving the zone B to carry with them an. amount of catalyst in excess of what would" normally be entrained in the, overhead gasstream, as indicated for example, in illusnative Iables IItoIV. This may be accomplished either by increasingthe gas velocity within the regeneration zone, or by decreasing the disengaging height of zone B so that the mouth of the overhead line 36 is nearer to the dense phase catalyst level 35. In the latter case the proximity of the dense phase bed to the zone of increasing velocity adjacent the outlet causes in- ,creased quantities of catalyst to be entrained in the gas stream. As an alternate arrangement for passing combined streams of catalyst and gases through the single cooler, a stream of catalyst may be withdrawn directly from the dense phase of the regenerator and passed to the inlet of the cooler 39, being united with the stream of gases and entrained catalyst withdrawn overhead from the zone B through line 36 and being passed in admixture therewith through the cooler. The dense phase catalyst stream may be withdrawn, for example, at a point in the catalyst standpipe I suitable to provide the pressure head necessary to raise the catalyst to the elevation of the cooler and introduce it into the stream passing through line 36. Applying this alternate arrangement to Fig. 3, the dense phase catalyst stream may be withdrawn from a standpipe such as standpipes I01 and I55.

Appended Table V sets forth suitable operating conditions in the application of this invention to a regeneration operation corresponding to the conversion operation outlined in Table I. Either of the systems illustrated in Figs. land 3 may be employed with but slight modification. It may be assumed that the apparatus comprising line 21, cooler 3|, and line 32 are eliminated from Fig. 1, or that lines I55 and I51 and cooler I58v are eliminated from Fig. 3.

Although Table V refers to an operation as applied to the apparatus of Fig. 3, it may be made to apply also to the apparatus of Fig. 1 by the proper substitution of equivalent elements. By removing the hundreds digit from each numeral of the table, the latter may be considered in connection with Fig. 1.

It will be seen from the foregoing description that the method of the present invention is comprised broadly of the steps: maintaining interface 35 at an elevation at which dilute phase withdrawn through line 36 contains the quantity of catalyst required for cooling dense phase 33; cooling the dilute phase mixture to a predetermined cooled catalyst temperature; separating cooled catalyst from the dilute phase mixture and accumulating it in a cooled catalyst hopper Pursuant thereto a stream of,

4'2 and recirculating cooled catalyst from the} cooled catalyst hopper 4-2 through valve ill-to dense phase 33 at a rate which maintains interface 35 and hints the temperature of dense phase 33 at the required values.

It is a preferred species of this method of op= eration that valve 50- be operated automatically to maintain interface 35 at a predetermined level.

It is still another preferred species of the invention to accomplish all of the cooling of dense phase 33 by means of cooler 39. However, it obvious that the method of the present inventionalso applies when some of the cooling for dense phase 33 is accomplished in some other, way than by heat exchange in cooler 39. For example, a substantially constant quantity of. heat may be abstracted from'the system by means of 3!, while cooler 39 is employed in accordance with the present method to vary the degree of additional cooling required.

While the preferred method of operation in accordance with the present invention contemplates theuse of the single cooler 39, or I39, for efiecting the desired temperature control within the regenerator, it is to be understood that this method of cooling the catalyst may be employed in conjunction with spent catalyst cooling, as by cooler 3i of Fig. 1 and with cooling of a recycle stream of dense phase catalyst from the regenerator, as by cooler I 58 of Fig. 3.

Table V Regenerator dimensions:

Zone A' Height ft 27.5 Diameter ft 23 Zone B' Height ft 14 Diameter ft 27 Spent catalyst (line I28) lbs./hr.. 623,490 Temp. spent catalyst (line I28) F 895 Recycled catalyst (line I5I) lbs./hr 662,000

We claim:

1. In a continuous process for the catalytic conversion of hydrocarbons wherein solid particles of a catalytic material and vapors of the hydrocarbons undergoing conversion are contacted in a conversion zone-and the spent catalyst particles are separated from the vaporous conversion products and regenerated for use in said con-' version zone by contacting them with an oxygen containing gas in a regeneration zone, which method includes passing said oxygen-containing gas upwardly through a mass of said catalyst in said regeneration zone at such a velocity that the solids in said zone are maintained in a fluidized state and an interface is maintained between a Tower dense phase and an upper light phase, the improvement which includes the steps of: withdrawing a stream of dense phase regenerated catalytic material from said regeneration zone and transferring it to said conversion zone; withdrawing dilute phase from said regeneration zone and cooling it; separating catalyst from said cooled dilute phase and accumulating a mass of cooled catalyst; and recirculating cooled catalyst from said mass of cooled catalyst to said dense phase at a rate sufficient to maintain said interface at a level at which said withdrawn dilute phase contains the quantity of catalyst required to be circulated for cooling.

2. A method as described in claim 1 in which the rate of recirculation of cooled catalyst from said mass of cooledcatalyst to said dense phase is automatically increased or decreased as the interface falls or rises respectively.

3. A method as described in claim 1 in which the rate of recirculation of cooled catalyst from said mass of cooled catalyst to said dense phase is automatically increased or decreased as the temperature'of said dense phase increases ol'fder creases respectively. "1 4". A method as described infclaim 1 in which said withdrawn dilute phase is cooled to a tem-- perature substantially lower than the temperature of said dense phase in said regeneration zone. 5. A method as described in claim 1 in which said withdrawn dilute phase is cooled to a -tem: perature not substantially greater than 650 F. JOSEPH W. MOORMAN.

LOUIS J. KELLY.

REFERENCES CITED The following references arevof record in the file of this patent:

UNITED STATES PATENTS 'Date Tyson Feb. 24, 1948 

1. IN A CONTINUOUS PROCESS FOR THE CATALYTIC CONVERSION OF HYDROCARBONS WHEREIN SOLID PARTICLES OF A CATALYTIC MATERIAL AND VAPORS OF THE HYDROCARBONS UNDERGOING CONVERSION ARE CONTACTED IN A CONVERSION ZONE AND THE SPENT CATALYST PARTICLES ARE SEPARATED FROM THE VAPOROUS CONVERSION PRODUCTS AND REGNENERATED FOR USE IN SAID CONVERSION ZONE BY CONTACTING THEM WITH AN OXYGENCONTAINING GAS IN A REGENERATION ZONE, WHICH METHOD INCLUDES PASSING SAID OXYGEN-CONTAINING GAS UPWARDLY THROUGH A MASS OF SAID CATALYST IN SAID REGENERATION ZONE AT SUCH A VELOCITY THAT THE SOLIDS IN SAID ZONE ARE MAINTAINED IN A FLUIDIZED STATE AND AN INTERFACE IS MAINTAINED BETWEEN A LOWER DENSE PHASE AND AN UPPER LIGHT PHASE, THE 